Face-hardened steel plate.



PATENTED DEC. 10, 1907.

G. DAVIS. FACE HARDENED STEEL PLATE. APPLICATION FILED APR 23 1902 Witnesses are .CLELAND DAVIS, OF TH UNITED s'rA'rEs NAvY, ASSIGNOR, BY MEsNE 'AssieNME'Nrs, 'ro CARNEGIE STEEL COMPANY, oFrIT'rsB Ro, PENNsYLvA IaA CORPORATION OF NEW JERSEY.

FACE-HARDENED STEEL PLATE.

To all whom it may concern:

Be it known that I, CLELAND DAVIS, lieutenant,'United States Navy, a'citizen of the United States, stationed atVVashington, in the District of Columbia, have invented certain new and useful Improvements in Face- HardenedSteel Plates, (Case E and I do hereby declare the following to be a full, clear, and exact descri tion of the invention, such'as will enable ot ers skilled in the art to which it appertains to make and use the same.

My invention relates to the, manufacture of a face hardened plate'of steel, which is uniformly impregnated with carbonto a rescribed depth, and in which the carbon shades off decrementally, or ina gradually decreasing manner, below said depth, the percentage of carbon in'that portion of the plate so impregnated. being greaterv than the normal content of the body of the plate.

In" my invention, the main objects to be obtained are first, to be able to-regulate the depth of carbonization and of chill so as t9 preserve the most effective proportion between the hard face and the tough,back; and

second,,at the same time to preserve the in tegral character of the metal throughout. 7

If the plate is heated by an electric furnace to any desired depth to a molten point or to one approaching fluidity, the back being kept comparatively cool, carbon can be introduced in the desired quantity and will be absorbed instantly or in a very short time; This carbon will be disseminated uniformly throughout the molten portion, and will shade away behindthat portion into the body of the plate.

In all the processes of ceinentation hitherto employed, the shading off of carbon begins from low it.

The accompanying drawings show the electric furnace described in my application,

Serial Number 55,124, filed April 10, 1901, of

which this isa division.

- in to my invention.

These drawin s show one form of furnace suitable for the hardening of a plate accord.-

he same arts are indicated by the same letters in hot the views. Figure 1 represents a section through a furnace constructed for carboniz ing armor plate, the-section of the cover being shown along the line 1 1 of'Fig. 2, and Fig. 2 rep- Specification of Letters Patent.

Divided and this application filed April 23. 1902. Serial No. 104.379

the surface or immediately be-" 'tric current is turned on.

A Patented Dec. 10, 1907.

entire plate should be insulatedin this or any other convenient Way.

1 D represents a removable cover which may be removed as by means of the cable E passing Over the pulleyF, or in any other convenient way. This cover makes an air tight joint over the side of the late to be treated. The said cover is packe with asbestos, or fire clay, or' similar material G, in which a plurality of electrodes H are held, and these electrodes are connected with the source of electricity by suitable-conductors indicated diagrammatically at I. The circuit to the source of electricity is completed by means of the contacts K and the conductors L.

The contacts K may be placed at suitable points on the sides or bottom of the plate.

'A'layer of powdered carbon M is interposed between the cover D and the face of theplatc to be heated. Air, either hot or cold, may be blown through the twyers a from any suitable air blast, not shown, and thus lower the temperature of the under side of the plate, while the upper-side of the plate is eing heated, or other means may be employed to keep the back of the plate cool, if preferred. v

In practice the plate is ut in position, a measured quantity of pow ered or granular carbon M is spread;over the surface to be treated, the cover D is lowered in place and the joints made tight, and the necessary cloc- This speedily raises the temperature of the carbon M and the upper partof the plate, until the latter reaches almost, if not uite, the fusing point,

measured degree of carburization may be obtained. Moreover, by varying the current I the cementation or hardening'of steelplates dent thatthis method of treatment: ma

and the timeoi itsapplication, the carbon may he carried through into the plate, causfing the cementa tion to be deeper than with the processes now in use. 4

cover the entire mass of carbon M, or a smgle' carbon electrode might be used, covering the entire face of theplate to be treated, or the electrodes H might be differently grouped, and the current passed through them seriatim, or ingrou s, 'or the pulverized carbon M might be time away with, and the carbon supplied direct from. the carbon electrodes, all or" which, and any othergrouping of electrodes I intend toinclude Within the scope of my claims.

Instead of having the circuit closed, I may establish an are between the electrodes and the face of the late to be treated, when dis integration of t he electrodes will supply the carbon. i

No hard and fast rule can be laid down as to the treatment of any particular class of plates, as the treatment would differ for'different grades of steel, and for diiierent ,sizes of plates, etc, butthe electrical characteristics once being established, it is evident that conditions can be reproduced with great accuracy by use of the volt meter and ammeter,

and by regulating the amount of carbon to be introduced into the plate. Ii/Will be evi-- be used withany plate or body of steel in w ich it is desired to surface harden. A

While I have described this invention as the rpose of face hardening the same, will e obvious that the sameis applicable-"to A direct current would, I believe, be prefthe compound I in presence of two applied to the -treatment of-armor plate-for v or bodies wherever it is desired to surface harden. It is obvious that both faces of the plate, or the entire surface of the body, may be hardened if desired. V B the Word integral in the claims, I intend to distinguish my product from one formed from twolor more plates, making up ate.

aving thus escribed my invention, what 'I claim and desire to secure by Letters Patent of the United States, is:

1. An integral mass of steel the face of which is uniformly impregnated .with absorbed carbon to a prescribed depth, the carbon decrementally shading off below that depth, tlfe percentage of the carbonin the portion of thaplate so impregnated being greater than the normal content of the body of the plate substantially as described.

2. A hard faced armor plate composed of an integral mass of steel having one face impregnat'ed with absorbed. carbon uniformly to a prescribed depth, and the carbon shading off decrementally below that depth, the percentage of carbon in the portion of the plate so impregnated being greater than the normal content. of the body. of the plate sub stantially as described.

3. An integral steel late having a surface portion orstratum 05 containing a substantiall uniform content of carbon'which is hi her t an the normal content of the plate body, and an underlying portion or stratum in which the carbon content shades off decrementally into the body of the plate; substantiall l as described.

' In testimony whereof, affix my signature,

witnesses. 4 CLELAND DAVIS. Witnesses:

CLARENCE A. BATEMAN, FRED W. ENGLERT.

determinable depth 

